The present invention relates to a holding ring for a blow mould for locking and/or fixing a plastics material pre-form with a support face for supporting a collar of the plastics material pre-form and a receiving cavity extending at a right angle to a main extension plane of the support face for receiving a neck region of the plastics material pre-form.
In particular, in the field of the beverage industry, plastic bottles have also been used as well as glass bottles for a considerable time already for the beverages to be poured in. In the production of these plastic bottles it is known to heat a plastics material blank, to supply it to a blow mould and then to blow it to its final size. To this end, use is generally made of blow moulds which are closed on their periphery around the blank to be blowed up and which are then supplied with compressed air through their opening.
In this case the aperture of the prospective bottle is already produced in the blank and it is preferably not treated further. For the actual blow moulding process a peripheral edge or collar of the blank rests upon a peripheral edge of the blow mould, so as to prevent the blank from falling into the interior of the blow mould.
In other words, as soon as a blow mould of this type is closed, the blank, i.e. the so-called pre-form, rests on the support face of the holding ring directly before the stretch blow moulding process.
In the shaping of the plastics material pre-form into the bottle, in particular two regions of the plastics material pre-form play a decisive role during the blow moulding procedure. On the one hand, a first region above the carrying ring is essential since this region may not change or scarcely change if possible. On the other hand, a second region below the holding ring should be defined which, starting from a “test-tube-shaped” body shape of the plastics material pre-form has to be reshaped into the bottle shape. During the blow moulding process an inner face of the plastics material pre-form is increased by a multiple, for example by a factor of twenty. At the same time a wall thickness decreases accordingly, for example by the same factor. This does not, however, take place to the same degree at all points on the plastics material pre-form. The region directly below the holding ring, i.e. below the collar, undergoes these stresses to the shortest degree. At this transition region a mouldability may occur which can be controlled only with difficulty and which increases (relax process without cooling of the neck plate) or reduces (normal re-shrinkage and optionally further components) a start of a bottle neck, for example in diameter in part.
Holding rings from the prior art for a blow mould, which are used for example during a blow moulding process, have the drawback, however, that a starting region of a neck directly below the collar of the plastics material pre-form changes in an undesired manner for example away from the collar in the direction of a longitudinal axis of the plastics material pre-form and undesired thickened portions of material can occur for example, as a result of which available neck handling systems cannot reliably convey the plastics material pre-forms or containers formed from them. In addition, an undesired higher weight of the plastics material pre-form can occur.
The object of the present invention is therefore to eliminate or at least to reduce the risk of undesired thickened portions of material in the neck region of a plastics material pre-form and at the same time to improve the manipulation of the plastics material pre-forms during and after the blow moulding.